Heretofore, a chewing gum of any type including a plate type and a bubble type has been prepared in two separate steps, namely the steps of gum base preparation and chewing gum preparation. In the first step of gum base preparation, gum base materials including natural resin such as chicle and jeltong, vinylacetate resin, polyisobutylene, ester gum, plasticizer, emulsifier, filler and others are kneaded for 3 to 4 hours per ton of materials by means of a usual open-kneader to produce a viscous gum base of a temperature ranging about 110.degree. to 120.degree. C. In the second step of chewing gum preparation, the gum base produced by the foregoing first step is kneaded with chewing gum additives including sugar, glucose, starch hydrolysate, artificial sweetener, flavor, coloring agent and others by means of a usual mixer for about 30 minutes per ton of materials to produce a chewing gum of a temperature ranging about 50.degree. to 60.degree. C. In the second step, preferably, the gum base produced by the first step and a half amount of sugar as well as starch hydrolysate are charged into the mixer and mixed, and then the remaining half amount of sugar and a softener are charged and thoroughly mixed. Finally, a flavor is added and trated for approximately one minute to produce a chewing gum. The chewing gum mass thus obtained through these two steps is subjected to a shaping process to produce various chewing gum products as disclosed in the U.S. Pat. Nos. 3,995,064 and 4,187,320.
In the conventional process hitherto exercised, a chewing gum has always been prepared through the two steps, namely steps of gum base preparation and chewing gum preparation. Up to date there has been no means to employ a single step process in lieu of the two step process. This is presumably due to the fact that the presence of sucrose and glucose in the severe kneading condition of the temperature of 110.degree. to 120.degree. C. for 3 to 4 hours required in the first step of gum base preparation causes thermal decomposition of the sugars, having an adverse effect on the quality of the chewing gum product.
As a result of diligent study for achieving simplification of the process for saving energy and improving quality of chewing gum, it has now been found out that the kneading of usual gum base materials with chewing gum additives under pressure by means of, for example, a pressurizing apparatus such as an intensive mixer, a Banbury mixer or a pressure-kneader (dispersion mixer) may provide a better and more brief operation (for example, within about 10 to 15 minutes) at about 40.degree. to 60.degree. C. in a single step without separating the gum base preparation step from the chewing gum preparation step, and yet can produce the chewing gums having uniform and improved quality.